The invention relates to cargo delivery vehicles. More particularly the invention relates to cargo delivery vehicles having multiple tiers of cargo storage which can be easily accessed from either street level or a raised-level dock.
It is desirable to store and transport a wide variety of cargo in vehicles having multiple storage tiers so that the most efficient use of the interior space in the vehicle can be made. In modern double drop trailers, the dropped areas fore and aft of the trailer axles may provide 12 feet or more of vertical storage space, offering the opportunity to transport two tiers of palletized cargo, each tier conventionally being approximately six feet in height.
When multi-tier storage is permitted by the interior height of the vehicle and the height of the cargo to be stored, the loading and unloading of the cargo present special problems. It is known to provide upper and lower fixed storage platforms in the vehicle, as described in U.S. Pat. No. 4,139,109 issued Feb. 13, 1989 to Murphy. With such an arrangement, loading and unloading cargo from ground level onto the lowermost storage platform is easily accomplished by the use of ramps, etc. However, loading the upper platforms may require mechanisms for lifting the cargo, such as a forklift or elevator. These may be external to and separate from the vehicle, or they may be designed to fold up inside the vehicle when not in use, as shown by Murphy. Conversely, if loading and unloading is to be performed from raised loading docks, it may be impractical to make use of the lowermost storage tier. Other disadvantages of such a system are that external lifts are cumbersome and exposed to the elements, and internal lift mechanisms take up valuable space which could otherwise be used for cargo storage. Regardless of whether these lift mechanisms are internal or external to the vehicle, the forward cargo is inaccessible while the aft cargo is in place.
A variety of specialized interior elevator arrangements have been developed to overcome the disadvantages of exterior lift mechanisms for multi-tier storage. For example, U.S. Pat. No. 2,832,636 issued Apr. 29, 1958 to Black, discloses the use of a single interior elevator platform extending the length of the cargo storage space, which enables the transportation of cargo in two tiers. Segmented platforms formed by multiple adjoining elevators have also been proposed, such as in U.S. Pat. No. 4,701,086 issued Oct. 20, 1987 to Thorndyke. These segmented platforms provide two-tier storage in certain segments and single-tier storage in other segments where tall cargo is to be stored.
But these vehicles with interior elevators suffer from the disadvantage that loading and unloading must both be performed at the lowermost level in order to achieve full utilization of the storage capacity. In many industries, the nature of the cargo delivery system requires that cargo be loaded at one level, or height, and unloaded from a different level, or height. In traditional transportation schemes, cargo is to be shipped between warehouses, affording the opportunity to both load and unload cargo from ground level at the point of origin and the destination, or at raised loading docks at both the origin and the destination. But modern distribution systems frequently require the transportation of cargo from a warehouse to the consumer's door. Examples are the express package delivery industry and the beverage and food service industries, both of which may permit loading from a raised warehouse loading dock, but require the vehicle's driver or his assistant to unload portions of cargo at the street level for delivery to individual customers at various points along the delivery route. Conversely, in industries such as the collection of recyclable materials, it would be desirable to load cargo portions at street level at various pick-up sites and unload the cargo all at once at a raised dock. Therefore, it is desirable to have a multi-tier delivery vehicle which can be fully loaded at one tier and fully unloaded at another tier. The single-plafform interior elevator assemblies disclosed by Black and Thorndyke do not offer this capability.
Furthermore, in these modern distribution systems just described, it is also desirable to load delivery vehicles from the rear at conventional dock height and unload cargo from the side of the delivery vehicle. Rather than a single destination for all of the cargo stored in the vehicle, there are often multiple destinations corresponding to various customers. Moreover, these varied distribution points typically lack loading docks, forklifts, or other facilities affording easy access to cargo positioned at conventional dock height. Instead, for reasons of safety and efficiency, it is highly desirable to eliminate the need for ramps and ladders by providing direct access to the cargo areas from curbside. To complete the delivery route, it may become necessary to unload all of the cargo from all storage tiers from the side of the vehicle.
But conventional enclosed delivery vehicles may not afford significant side access due to the structural requirements placed on the side walls of the trailer. In conventional enclosed trailers having single-tier or multi-tier storage, the floor is typically required to bear the weight of the cargo and transfer those forces via the side walls to the vehicle's axles. The requirement for numerous, regularly spaced structural members in the side walls may limit the availability of sizable doors for cargo access from the side of the vehicle. Some conventional vehicles, having floors running continuously over the axles and positioned to conveniently receive cargo at warehouse dock level, offer limited side access through doors penetrating the side walls, but the structural integrity of such vehicles may be drastically reduced. Moreover, to make use of such side doors, drivers may be required to climb a ladder from street level up to the side door, bend over into the interior of the vehicle to reach the cargo, and then descend the ladder while carrying heavy cargo. Such an arrangement presents a significant risk of injury or exhaustion of the vehicle's driver.
Another potential disadvantage of conventional, structural side walls is that insulating foam for heated or refrigerated storage compartments must be inserted between the rigid, thermally conductive steel or aluminum framing in the walls, thereby permitting thermal "leaks" in the side walls. Therefore, it is desirable to minimize or eliminate the structural requirements of the side walls of the delivery vehicle to afford side access to the cargo and to permit the use of non-structural, lightweight pre-fabricated insulating panels placed external to all framing.
Moreover, the load-bearing floor is typically required to be quite thick for adequate structural support. Because the ground clearance for such trailers is often fixed by regulation, a thick floor decreases the interior space available for storage. Therefore, it is also desirable to minimize or eliminate the load-bearing requirements of the floor of the delivery vehicle in order to maximize interior storage space, especially space located in the ergonomically advantageous lower zone of the trailer, accessible to a loader or unloader standing at the street level.
Accordingly, it is an object of the present invention to provide multi-tier cargo storage in a delivery vehicle.
It is a further object of the invention to provide a multi-tier delivery vehicle which can be both loaded and unloaded from a single, selectable storage tier.
A still further object of the invention is to provide a multi-tier delivery vehicle which can be loaded at a first storage tier and unloaded at a second, different storage tier.
A still further object of the invention is to provide a multi-tier delivery vehicle which can be loaded from the rear and unloaded from either side or, conversely, can be loaded from either side and unloaded from the rear.
A still further object of the invention is to provide a multi-tier delivery vehicle which can be loaded from the rear at a first storage tier and unloaded from the side at a second, different storage tier.
A still further object of the invention is to provide a multi-tier delivery vehicle that can be unloaded at street level by the driver or his assistant without subjecting them to undue strain or injury.
A still further object of the invention is to provide a multi-tier delivery vehicle in which the load-bearing requirements placed on the side walls and floors is substantially reduced, permitting greater side access to the cargo, allowing the use of inexpensive and readily available insulating panels to form a continuous thermal barrier in the side walls, and maximizing internal storage space.